Image pickup apparatus and image pickup unit having device for removing foreign substance deposited on surface of optical member

ABSTRACT

An image pickup unit integrally includes an optical lowpass filter, a piezoelectric element, and an image pickup element. The optical lowpass filter is separated into a plurality of grouped optical members in an imaging light axis direction. The optical lowpass filter includes first to third grouped optical members. To remove a foreign substance, such as dust or dirt, deposited on the surface of the first grouped optical member, the piezoelectric element vibrates the first grouped optical member. The first grouped optical member has a monocrystalline structure having a Q value indicating the sharpness of resonance higher than that of glass, which is an amorphous material, and a low attenuation characteristic so as to efficiently vibrate the first grouped optical member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an image pickup apparatusand, in particular, to technology for removing a foreign substancedeposited on a surface of an optical member disposed along an imaginglight axis.

2. Description of the Related Art

Image pickup apparatuses, such as digital cameras, that capture an imageby converting an image signal into an electrical signal receive lightusing an image pickup element, such as a charged coupled device (CCD) ora complementary metal oxide semiconductor (CMOS) sensor. The imagepickup apparatuses convert a photoelectrically converted signal outputfrom the image pickup element to image data. Thereafter, the imagepickup apparatuses store the image data on a recording medium, such as amemory card. In such image pickup apparatuses, an optical lowpass filterand an infrared cut filter are disposed on the front side (an objectside) of the image pickup element.

If a foreign substance, such as dust or dirt, is deposited on surfacesof the cover glass of the image pickup element or these filters, theforeign substance generates a black spot in a captured image, andtherefore, the quality of the image deteriorates.

In particular, since digital single-lens reflex cameras withinterchangeable lenses include a mechanical operating unit, such as ashutter and a quick-return mirror, disposed in the vicinity of an imagepickup element, a foreign substance, such as dust or dirt, is possiblygenerated by the operating unit and is deposited on the surfaces of thecover glass of the image pickup element and the filters. In addition,when the lens is changed, a foreign substance may enter inside thecamera body from the opening of a lens mount and may be deposited on thesurfaces of the cover glass of the image pickup element and the filters.

Japanese Patent Laid-Open No. 2003-319222 (corresponding to U.S. Pat.No. 2003-202114 A1) describes technology in which a dust-proof memberthat allows an imaging light beam to pass therethrough is disposed onthe object side of an image pickup element and is vibrated by means of apiezoelectric element, and therefore, a foreign substance deposited onthe surface of the dust-proof member is removed.

In such a structure in which a foreign substance deposited on thesurface of an optical member can be removed by vibrating the opticalmember, a biasing force may be applied to the optical member by means ofa biasing member in addition to vibrating the optical member by means ofthe piezoelectric element.

In Japanese Patent Laid-Open No. 2003-319222, in order to remove aforeign substance deposited on the surface of the dust-proof member, avoltage is applied to a piezoelectric element coupled with thedust-proof member so as to drive the piezoelectric element. Thus, thedust-proof member is displaced in the light axis direction so as toproduce membrane oscillation.

However, in this case, a special member, that is, the dust-proof memberneeds to be disposed on the imaging light axis. Therefore, the layout ofthe members is restricted. In addition, the optical functionality andoptical performance, such as the transmittance for an imaging lightbeam, disadvantageously deteriorate.

SUMMARY OF THE INVENTION

The present invention is directed to an image pickup apparatus capableof efficiently removing a foreign substance, such as dust or dirt,deposited on a surface of an optical member without utilizing anadditional dust-proof member on the imaging light axis.

According to an aspect of the present invention, an image pickupapparatus includes an image pickup element configured to convert anoptical image of an object into an electrical signal, an optical memberdisposed in front of the image pickup element, the optical memberincluding a plurality of grouped sub-optical members, including a firstgrouped sub-optical member, that are separated in an imaging light axisdirection, and a vibrating unit configured to vibrate the first groupedsub-optical member disposed at a forefront position in the opticalmember. The first grouped sub-optical member is formed from amonocrystalline plate.

According to another aspect of the present invention, an image pickupunit included in an image pickup apparatus integrally includes an imagepickup element configured to convert an optical image of an object intoan electrical signal, an optical member disposed in front of the imagepickup element, the optical member including a plurality of groupedsub-optical members, including a first grouped sub-optical member, thatare separated in an imaging light axis direction, and a vibrating unitconfigured to vibrate the first grouped sub-optical member disposed at aforefront position in the optical member. The first grouped sub-opticalmember is formed from a monocrystalline plate.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a digital single-lens reflexcamera according to an embodiment of the present invention.

FIG. 2 is a rear perspective view of a digital single-lens reflex cameraaccording to the embodiment of the present invention.

FIGS. 3A and 3B are block diagrams illustrating an exemplary electricalconfiguration of the digital single-lens reflex camera according to theembodiment of the present invention.

FIG. 4 is an exploded perspective view illustrating the internalstructure of the digital single-lens reflex camera including an imagepickup unit.

FIG. 5 is a front view of the image pickup unit.

FIG. 6 is an exploded perspective view of the image pickup unit.

FIG. 7 is a front view illustrating a positional relationship betweenthe image pickup unit and a body chassis.

FIG. 8 is a longitudinal cross-sectional view of a camera including theimage pickup unit.

FIG. 9A is a perspective view of a biasing member and a biasing-memberholding unit when viewed from the object side before the biasing memberand the biasing-member holding unit are assembled together.

FIG. 9B is a top view of the biasing member and the biasing-memberholding unit after the biasing member and the biasing-member holdingunit are assembled together.

FIGS. 9C and 9D are side views illustrating a relationship between thebiasing member and the piezoelectric element.

FIG. 10 is a concept diagram illustrating a Q value.

FIG. 11 is a transverse cross-sectional view of the image pickup unit.

FIG. 12A is a front view illustrating a vibration transfer member and abiasing force transfer member.

FIG. 12B is a side view illustrating the vibration transfer member andthe biasing force transfer member.

FIG. 13 is a diagram illustrating a floating structure of an imagepickup element holding member and a lowpass filter holding member.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described in detail withreference to the accompanying drawings.

FIGS. 1 and 2 are external views of a digital single-lens reflex cameraaccording to an embodiment of the present invention. FIG. 1 is a frontperspective view of the digital single-lens reflex camera when viewedfrom the object side. FIG. 2 is a rear perspective view of the digitalsingle-lens reflex camera when viewed from the photographer side.

As shown in FIG. 1, a camera body 1 has a grip portion 1 a extendingtowards an object so that a photographer can stably hold the camera whentaking a photo.

An objective taking lens unit (not shown in FIGS. 1 and 2) is removablymounted on a lens mount 2 of the camera body 1. A mount contact 21allows the camera body 1 to exchange a control signal, a status signal,and a data signal with the objective taking lens unit. In addition,electrical power is supplied from the camera body 1 to the objectivetaking lens unit via the mount contact 21. The mount contact 21 may beconfigured so as to allow light communication and audio communication inaddition to electrical communication between the camera body 1 and theobjective taking lens unit. A lens lock release button 4 is disposed onthe side surface of the lens mount 2. The lens lock release button 4 ispressed in order to remove the objective taking lens unit from thecamera body 1.

The camera body 1 incorporates a mirror box 5 that leads an imaginglight beam that has passed through the objective taking lens unit. Themirror box 5A includes a main mirror (quick-return mirror) 6. The mainmirror 6 is disposed at an angle of 45° with respect to an imaging lightaxis so as to lead the imaging light beam to a penta-dach mirror 22 (seeFIG. 3). The main mirror 6 can be moved away from that position to aposition so that the imaging light beam is led to an image pickupelement 33 (see FIG. 3).

A release button 7, a main operation dial 8, and a top operation modesetting button 10 are disposed on the upper surface of the camera body 1on the side of the grip portion 1 a. The release button 7 is used as aswitch for starting an image capturing operation. The main operationdial 8 is used for setting a shutter speed and a lens aperture value inaccordance with a mode of the image capturing operation. The topoperation mode setting button 10 is used for determining varioussettings of an image pickup system. Some of the operation results ofthese operation members are displayed on an LCD panel 9. A first lighttouch of the release button 7 turns on a switch-SW1 7 a (see FIG. 3) anda second light touch turns on a switch-SW2 7 b (see FIG. 3). The topoperation mode setting button 10 is used for determining whether onepush of the release button 7 causes continuous shooting or singleshooting. In addition, the top operation mode setting button 10 is usedfor setting a self-timer mode. The settings can be displayed on the LCDpanel 9.

A strobe unit 11 that pops up from the camera body 1, a shoe groove 12in which a flash unit is mounted, and a flash contact 13 are disposed onthe upper surface of the camera body 1 in the central area.

A shooting mode setting dial 14 is disposed on the upper surface of thecamera body 1 in the right area.

An openable cover 15 for covering external terminals is disposed on theside surface of the camera body 1 opposite to the side surface havingthe grip portion 1 a thereon. Inside the cover 15, a video signal outputjack 16 and a universal serial bus (USB) output connector 17 aredisposed.

As shown in FIG. 2, a finder eyepiece 18 is disposed on a back surfaceof the camera body 1 in an upper area. In addition, a color liquidcrystal monitor 19 is disposed on the back surface of the camera body 1in substantially the central area. The color liquid crystal monitor 19can display an image.

A sub operation dial 20 is disposed adjacent to the color liquid crystalmonitor 19. The sub operation dial 20 plays an auxiliary role of themain operation dial 8. For example, in an AE mode of the camera, the suboperation dial 20 is used for setting an exposure correction value inorder to change the exposure value from the optimal exposure valuedetermined by an automatic exposure unit. In a manual mode in which auser determines a shutter speed and an aperture value of the lens, theshutter speed is determined by using the main operation dial 8 and theaperture value of the lens is determined by using the sub operation dial20. In addition, the sub operation dial 20 is used for selecting acaptured image to be displayed on the color liquid crystal monitor 19.

Furthermore, a main switch 43 for starting and stopping the operation ofthe camera and a cleaning instruction operation member 44 are disposedon the back surface of the camera. As described in more detail below,the cleaning instruction operation member 44 is used for instructing thecamera to vibrate a lowpass filter so as to remove dust or dirtdeposited on the surface of the lowpass filter.

FIG. 3 is a block diagram of an exemplary electrical configuration of adigital single-lens reflex camera according to the present embodiment.Similar numbering will be used for describing similar components in FIG.3 as was utilized above in describing FIGS. 1 and 2. A centralprocessing unit (hereinafter referred to as an “MPU”) 100 of amicrocomputer incorporated in the camera body 1 performs overall controlof the camera. The MPU 100 performs a variety of processing forcomponents of the camera and processes a variety of instructions. Anelectrically erasable programmable read-only memory (EEPROM) 100 a canstore time information output from a time measurement circuit 109 andadditional information.

A mirror driving circuit 101, a focus detection circuit 102, a shutterdriving circuit 103, an image signal processing circuit 104, a switchsensing circuit 105, and a metering circuit 106 are connected to the MPU100. In addition, an LCD driving circuit 107, a battery check circuit108, the time measurement circuit 109, a power supply circuit 110, and apiezoelectric element driving circuit 111 are connected to the MPU 100.These circuits operate under the control of the MPU 100.

The MPU 100 communicates with a lens control circuit 201 in theobjective taking lens unit via the mount contact 21. When the objectivetaking lens unit is mounted on the camera body 1, the mount contact 21sends a signal to the MPU 100. Thus, the lens control circuit 201communicates with the MPU 100 so as to drive an objective taking lens200 and an aperture 204 disposed in the objective taking lens unit viaan AF driving circuit 202 and an aperture driving circuit 203. Note thatalthough, for simplicity, the objective taking lens unit includes onlyone objective taking lens 200 in FIG. 3, the objective taking lens unitcan include a plurality of lens groups in practice.

The AF driving circuit 202 includes, for example, a stepping motor. TheAF driving circuit 202 changes the position of a focus lens in theobjective taking lens 200 using control performed by the lens controlcircuit 201 so that the imaging light beam is focused on the imagepickup element 33. The aperture driving circuit 203 includes, forexample, an auto iris. The aperture driving circuit 203 changes theaperture 204 using the lens control circuit 201 so that an opticalaperture value is obtained.

As shown in FIG. 3, the main mirror 6 is disposed at an angle of 45°with respect to the imaging light axis and leads the imaging light beamthat has passed through the objective taking lens 200 to the penta-dachmirror 22. In addition, the main mirror 6 allows a part of the imaginglight beam to pass therethrough and leads the part of the imaging lightbeam to a sub-mirror 30. The sub-mirror 30 leads the part of the imaginglight beam that has passed through the main mirror 6 to a focusdetection sensor unit 31.

The mirror driving circuit 101 includes, for example, a DC motor and agear train. The mirror driving circuit 101 drives the main mirror 6 tomove to a position at which a user can observe an object image through afinder or a position at which the main mirror 6 moves away from theimaging light beam. When the main mirror 6 is driven, the sub-mirror 30moves to a position at which the imaging light beam is led to the focusdetection sensor unit 31 or a position at which the sub-mirror 30 movesaway from the imaging light beam.

The focus detection sensor unit 31 includes a field lens disposed in thevicinity of an imaging plane (not shown), a reflecting mirror, asecondary imaging lens, an aperture, and a line sensor including aplurality of charge-coupled devices (CCDs). The focus detection sensorunit 31 performs focus detection using a phase difference method. Asignal output from the focus detection sensor unit 31 is delivered tothe focus detection circuit 102. Thereafter, the signal is converted toan object image signal and is delivered to the MPU 100. The MPU 100performs a focus detection computation based on a phase differencemethod using the object image signal. Thus, the MPU 100 determines anamount of defocus and a defocus direction. Subsequently, the MPU 100moves the focus lens in the objective taking lens 200 to a focal pointthrough the lens control circuit 201 and the AF driving circuit 202using the determined amount of defocus and defocus direction.

The penta-dach mirror 22 reflects the imaging light beam reflected offthe main mirror 6 so that an erected image is formed. The photographercan observe the object image from the finder eyepiece 18 through thefinder optical unit. In addition, the penta-dach mirror 22 leads a partof the imaging light beam to a metering sensor 23. Upon receipt of anoutput of the metering sensor 23, the metering circuit 106 converts theoutput to luminance signals of partitioned areas of the observationplane, which are output to the MPU 100. The MPU 100 computes theexposure value using the luminance signals.

A shutter (mechanical focal plane shutter) unit 32 blocks the imaginglight beam when the camera is ready for shooting, that is, when thephotographer views the object image through the finder. To capture theimage, the shutter unit 32 operates in response to a release signal sothat a desired exposure time period is obtained using a time differencebetween a time a first blade group (not shown) starts and a time asecond blade group (not shown) starts. The shutter unit 32 is controlledby the shutter driving circuit 103 in response to an instruction fromthe MPU 100.

An image pickup unit 400 includes an optical lowpass filter 410, apiezoelectric element 430, and the image pickup element 33, which areintegrated into one unit. The image pickup unit 400 will be described inmore detail below.

As shown in FIG. 6, the optical lowpass filter 410 is separated into aplurality of substantially rectangular members, that is, a first groupedoptical member 411, a second grouped optical member 412, and a thirdgrouped optical member 413. According to the present embodiment, thefirst grouped optical member 411 is formed from a quartz birefringentplate. The second grouped optical member 412 is formed from a phaseplate laminated on infrared absorption glass. The third grouped opticalmember 413 is formed from a quartz birefringent plate. As used herein,the term “grouped” indicates that a member that seems to be a single onewhen externally viewed may have a layered structure. For example, thesecond grouped optical member 412 has a layered structure. Therefore,according to the present embodiment, although the first grouped opticalmember 411 is a quartz birefringent plate which is a monocrystallineplate, each of the second grouped optical member 412 and the thirdgrouped optical member 413 may be a monocrystalline plate laminated onanother monocrystalline plate or a monocrystalline plate laminated on aglass plate having no crystal structure. In addition, a coatingproviding certain optical functionality may be applied to the surface ofeach of the optical members 411 to 413. For example, to reflect aninfrared light ray or an ultraviolet (UV) ray, SiO₂ and TiO₂ can bealternately coated on the surface of each of the grouped optical members411 to 413.

The piezoelectric element 430 is driven by the piezoelectric elementdriving circuit 111 in response to an instruction from the MPU 100. Thepiezoelectric element 430 vibrates the first grouped optical member 411which is a forefront member (closest to the object) in the opticallowpass filter 410.

According to the present embodiment, the image pickup element 33 is aCMOS image pickup device. However, a CCD may be used for the imagepickup element 33. Any type of image pickup device can be used for theimage pickup element 33.

A clamp/correlated double sampling (CDS) circuit 34 performs basicanalog processing on a signal before the signal is A/D-converted. Theclamp/CDS circuit 34 can change the clamp level. An automatic gaincontrol (AGC) device 35 also performs basic analog processing on asignal before the signal is A/D-converted. The AGC device 35 can changeeven a basic AGC level. An analog-to-digital (A/D) converter 36 convertsan analog signal output from the image pickup element 33 to a digitalsignal.

The image signal processing circuit 104 performs general hardware-basedimage processing, such as a gamma/knee process, a filtering process, andan information composing process for a monitor display, on digital imagedata. The image signal processing circuit 104 outputs image data for amonitor display. The image data is displayed on the color liquid crystalmonitor 19 via a color liquid crystal driving circuit 112. In addition,the image signal processing circuit 104 can store the image data in abuffer memory 37 via a memory controller 38 in response to aninstruction from the MPU 100. Furthermore, the image signal processingcircuit 104 can compress the image data, for example, in a JPEG format.When images are continuously captured, as in a continuous shooting mode,the image signal processing circuit 104 temporarily stores the imagedata in the buffer memory 37, and subsequently, can sequentially readout the unprocessed image data from the buffer memory 37 via the memorycontroller 38. In this way, the image signal processing circuit 104 cansequentially perform image processing and compression processingregardless of the input speed of the image data input from the A/Dconverter 36.

The memory controller 38 stores image data input from an externalinterface 40 in a memory 39. In addition, the memory controller 38outputs the image data stored in the memory 39 through the externalinterface 40. Note that the video signal output jack 16 and the USBoutput connector 17 shown in FIG. 1 correspond to the external interface40. For example, a flash memory that is removably disposed in the camerabody 1 is used for the memory 39.

The switch sensing circuit 105 transmits a signal input in accordancewith the operating state of a switch to the MPU 100. The switch-SW1 7 ais turned on by a first light touch of the release button 7. Theswitch-SW2 7 b is turned on by a second light touch of the releasebutton 7. When the switch-SW2 7 b is turned on, an instruction to startshooting is transmitted to the MPU 100. The main operation dial 8, thesub operation dial 20, the shooting mode setting dial 14, the mainswitch 43, and the cleaning instruction operation member 44 areconnected to the switch sensing circuit 105.

The LCD driving circuit 107 drives the LCD panel 9 and a finder liquidcrystal display unit 41 in response to an instruction from the MPU 100.

The battery check circuit 108 checks the level of a battery in responseto an instruction from the MPU 100 and transmits the checked level tothe MPU 100. A power supply unit 42 supplies electrical power to each ofthe components of the camera.

The time measurement circuit 109 measures a time period from a time themain switch 43 is turned off to a time the main switch 43 is turned onand the date and time. The time measurement circuit 109 transmits themeasured result to the MPU 100 in response to an instruction from theMPU 100.

The image pickup unit 400 is described next. FIG. 4 is an explodedperspective view illustrating the internal structure of the cameraincluding the image pickup unit 400. The shutter unit 32, a body chassis300, which is a structural member of the camera body 1, and the imagepickup unit 400 are assembled on the mirror box 5 in this order from theobject side. The image pickup unit 400 is assembled on the mirror box 5so that a distance between the imaging surface of the image pickupelement 33 and a mounting surface of the lens mount 2, which is amounting reference of the objective taking lens unit, is a predeterminedvalue, and the imaging surface of the image pickup element 33 isparallel to the mounting surface of the lens mount 2. An eyepiece unit210 including the penta-dach mirror 22 and the finder eyepiece 18 isdisposed on the upper section of the body chassis 300. Thus, thephotographer can view an optical image of an object led by the mainmirror 6 and the penta-dach mirror 22 in the mirror box 5. The eyepieceunit 210 is mounted on an eyepiece-unit locking unit 300 a and is lockedby a locking member 301. The eyepiece-unit locking unit 300 a is formedby bending the upper portion of the body chassis 300 and extending thatportion.

FIG. 5 is a front view of the image pickup unit 400. FIG. 6 is anexploded perspective view of the image pickup unit 400. As shown in FIG.6, the image pickup unit 400 includes an image pickup element unit 500and a lowpass filter unit 470 as main components.

The image pickup element unit 500 includes at least the image pickupelement 33 and an image pickup element holding member 510. The lowpassfilter unit 470 includes at least the first grouped optical member 411,a lowpass filter holding member 420, the piezoelectric element 430, avibration transfer member 431, a biasing member 440, a biasing forcetransfer member 441, a first resilient member 480, a second resilientmember 490, a regulation member 460, and a mask member 560.

In the image pickup element unit 500, the image pickup element holdingmember 510 is a plate having a substantially rectangular opening. Theimage pickup element 33 is fixed to the image pickup element holdingmember 510 so that the imaging plane of image pickup element 33 isexposed through the opening. To fix the image pickup element holdingmember 510 to the mirror box 5 by means of screws, an arm portion isformed so as to extend from the periphery of the image pickup elementholding member 510. The image pickup element holding member 510 is fixedto the mirror box 5 by means of screws at three points.

In the lowpass filter unit 470, the lowpass filter holding member 420has a frame-like shape and is formed from resin or metal. The firstgrouped optical member 411 is attached to a frame portion 420 a of thelowpass filter holding member 420. In this case, the first resilientmember 480 having a ring shape is disposed between the lowpass filterholding member 420 and the first grouped optical member 411. An armportion 420 b is integrally formed at each of the four corners of thelowpass filter holding member 420. Thus, the lowpass filter holdingmember 420 is attached to the image pickup element holding member 510and is supported by the image pickup element holding member 510.

To hold the piezoelectric element 430, a container portion 421 is formedon one of the four sides (an upper side) of the frame portion 420 a ofthe lowpass filter holding member 420. One end surface of thepiezoelectric element 430 is bonded to the frame portion 420 a by anadhesive agent so that a direction in which the piezoelectric element430 extends when a voltage is applied thereto is perpendicular to theimaging light axis (i.e., the vertical direction of the camera). Thepiezoelectric element 430 is electrically connected to the piezoelectricelement driving circuit 111 via a lead wire 432 and a connector 433.

The vibration transfer member 431 is sandwiched by the piezoelectricelement 430 and the first grouped optical member 411 and is bonded tothe first grouped optical member 411. In this case, the piezoelectricelement 430 is not fixed to the vibration transfer member 431 that isfixed to the first grouped optical member 411. The piezoelectric element430 is only in contact with the vibration transfer member 431. Thematerial, shape, and effect of the vibration transfer member 431 aredescribed later with reference to FIGS. 12A and 12B.

The biasing member 440 that is held by a biasing-member holding unit 450is attached to one of four sides (a lower side) of the frame portion 420a of the lowpass filter holding member 420. The lower side is oppositeto the side on which the container portion 421 is formed. The biasingmember 440 urges the first grouped optical member 411 towards thepiezoelectric element 430.

The biasing force transfer member 441 is sandwiched by the biasingmember 440 and the first grouped optical member 411. The biasing forcetransfer member 441 is bonded to the first grouped optical member 411.The material, shape, and effect of the biasing force transfer member 441are described later with reference to FIGS. 12A and 12B.

That is, the first grouped optical member 411 is disposed so as to besandwiched by the piezoelectric element 430 and the biasing member 440in the same plane via the vibration transfer member 431 and the biasingforce transfer member 441, respectively. Due to such an arrangement, thefirst grouped optical member 411 can move while following the expansionand contraction of the piezoelectric element 430.

The piezoelectric element 430 is a layered piezoelectric element inwhich a piezoelectric member and an internal electrode are alternatelylayered. The piezoelectric element 430 is disposed so as to be incontact with the vibration transfer member 431. More specifically, ad33-type layered piezoelectric element is employed. For a d33-typelayered piezoelectric element, a voltage is applied in a direction inwhich the piezoelectric members are layered. Accordingly, a largeamplitude (a large displacement) can be obtained in the layer direction,and therefore, the first grouped optical member 411 can be largelydisplaced in the layer direction. Alternatively, a variety of types ofpiezoelectric elements can be used. That is, any piezoelectric elementthat can displace the optical lowpass filter 410 in a direction parallelto the plane of the optical lowpass filter 410 (a directionperpendicular to the imaging light axis) can be used.

The biasing member 440 is a block-shaped resilient member. The biasingmember 440 is disposed so as to face the piezoelectric element 430 andbe in contact with the biasing force transfer member 441. The biasingmember 440 is supported by the biasing-member holding unit 450. FIG. 9Ais a perspective view of the biasing member 440 and the biasing-memberholding unit 450 when viewed from the object side before the biasingmember 440 and the biasing-member holding unit 450 are assembledtogether. FIG. 9B is a top view of the biasing member 440 and thebiasing-member holding unit 450 after the biasing member 440 and thebiasing-member holding unit 450 are assembled together. FIGS. 9C and 9Dare side views illustrating a relationship between the biasing member440 and the piezoelectric element 430.

As shown in FIGS. 9A and 9B, protrusions 450 a are formed on the surfaceof the biasing-member holding unit 450 on the object side at twolocations. Depressions 440 a are formed on the surface of the biasingmember 440 on the object side at two locations. The protrusions 450 a ofthe biasing-member holding unit 450 are engaged with the depressions 440a of the biasing member 440. When the biasing member 440 is assembled tothe biasing-member holding unit 450, the position of the biasing member440 can be determined by engaging the protrusions 450 a with thedepressions 440 a. In addition, by providing the protrusions 450 a, whenthe biasing member 440 is pressed and deformed, the deformation of thebiasing member 440 does not interfere with the shutter unit 32 disposedon the object side of the biasing member 440.

Additionally, depressions 440 b are formed on the surface of the biasingmember 440 on the photographer side at three locations. The reason whythe depressions 440 b are formed on the surface of the biasing member440 on the photographer side is to keep cross-sectional areasperpendicular to a biasing direction on the front and rear side (theobject side and the photographer side) of a center plane 411 a of thefirst grouped optical member 411, where the plane 411 a is perpendicularto the imaging light axis, the same as the cross-sectional area of thecenter plane 411 a. In contrast, protrusions 450 b are formed on thebiasing-member holding unit 450 at three locations. The protrusions 450b can be engaged with the depressions 440 b.

In the case where a cross-sectional area of the biasing member 440 thatis perpendicular to the biasing direction changes on the front and rearsides of the center plane 411 a, when, as shown in FIG. 9D, the biasingmember 440 is pressed by the biasing force transfer member 441, amountsof contraction of the biasing member 440 are different on the objectside and the photographer side. Accordingly, the biasing force transfermember 441 is tilted in the biasing direction, and therefore, the firstgrouped optical member 411 is tilted with respect to the lowpass filterholding member 420 and the first resilient member 480. If the firstgrouped optical member 411 is largely tilted, a space is generatedbetween the first grouped optical member 411 and the first resilientmember 480 or between the lowpass filter holding member 420 and thefirst resilient member 480. Thus, a foreign substance maydisadvantageously enter inside the camera through the space.

In contrast, according to the present embodiment, the cross-sectionalareas of the biasing member 440 are substantially the same on the frontand rear sides of the center plane 411 a. Therefore, as shown in FIG.9C, even when the biasing member 440 is pressed by the biasing forcetransfer member 441, the amounts of contraction of the biasing member440 are substantially the same on the front and rear sides.Consequently, the first grouped optical member 411 is not largely tiltedwith respect to the lowpass filter holding member 420 and the firstresilient member 480. As a result, the interfaces between the firstgrouped optical member 411 and the first resilient member 480 andbetween the lowpass filter holding member 420 and the first resilientmember 480 can be sealed, thus preventing a foreign substance, such asdust or dirt, from entering inside the camera.

According to the present embodiment, the biasing member 440 is made froma rubber. However, the biasing member 440 may be made from any resilientmaterial. For example, the biasing member 440 may be made from a highmolecular weight polymer, such as rubber or plastic. Alternatively, thebiasing member 440 may be made from a metal leaf spring or a metal coilspring. Alternatively, the lowpass filter holding member 420 may beresilient so that the first grouped optical member 411 moves whilefollowing the expansion and contraction of the piezoelectric element430.

Referring back to FIGS. 5 and 6, the first resilient member 480 disposedbetween the lowpass filter holding member 420 and the first groupedoptical member 411 is formed from an elastomer (a polymeric material).The first resilient member 480 allows the first grouped optical member411 to vibrate while following the expansion and contraction of thepiezoelectric element 430. In addition, the first resilient member 480prevents the first grouped optical member 411 from being damaged by thevibration. The interface between the first grouped optical member 411and the lowpass filter holding member 420 is sealed at the four sidesusing the first resilient member 480.

The first grouped optical member 411 is supported by the first resilientmember 480 and the second resilient member 490, which is described inmore detail below, so as to move in the imaging light axis directionwithin a predetermined range. That is, when the first grouped opticalmember 411 receives the vibration of the piezoelectric element 430, thefirst grouped optical member 411 is allowed to tilt from a planeperpendicular to the imaging light axis at an angle of a few degrees.Since an inclination of a few degrees is allowed, a foreign substancedeposited on the surface of the first grouped optical member 411 issubjected to acceleration in the imaging light axis direction. Thus, theforeign substance can be further easily removed.

However, in the case where an inclination of the first grouped opticalmember 411 is allowed with respect to a plane perpendicular to theimaging light axis, if the piezoelectric element 430 is bonded and fixedto the first grouped optical member 411, a shearing stress is generatedin the piezoelectric element 430. In particular, since a layeredpiezoelectric element is used in the present embodiment, the shearingstress easily damages the piezoelectric element.

To address this issue, the surface (vibration surface) of thepiezoelectric element 430 that is in contact with the first groupedoptical member 411 (the vibration transfer member 431) is not bonded tothe first grouped optical member 411 (the vibration transfer member431). That is, the surface (vibration surface) of the piezoelectricelement 430 is only in contact with the first grouped optical member 411(the vibration transfer member 431). In this way, even when the biasingforce transfer member 441 is tilted from a plane perpendicular to theimaging light axis, a shearing stress is not applied to thepiezoelectric element 430. This is because when the first groupedoptical member 411 is tilted, the contact surface of the piezoelectricelement 430 is only shifted from the contact surface of the firstgrouped optical member 411 (the vibration transfer member 431) in termsof position, and a rotation force is not directly applied to thepiezoelectric element 430.

However, when the contact surface of the piezoelectric element 430 isnot bonded to the contact surface of the first grouped optical member411 (the vibration transfer member 431), the compliance of the firstgrouped optical member 411 in response to the vibration of thepiezoelectric element 430 disadvantageously deteriorates.

To address this issue, as noted above, the first grouped optical member411 is disposed so as to be sandwiched by the piezoelectric element 430and the biasing member 440 in the same plane. That is, by urging thefirst grouped optical member 411 from the opposite side of thepiezoelectric element 430, the first grouped optical member 411 (thevibration transfer member 431) is in contact with the piezoelectricelement 430 even when the piezoelectric element 430 is driven in adirection in which the piezoelectric element 430 contracts.

Such a structure provides excellent compliance of the first groupedoptical member 411 in response to the vibration of the piezoelectricelement 430 without damaging the piezoelectric element 430 caused by anoccurrence of a shearing stress.

As shown in FIG. 6, the regulation member 460 is disposed on the objectside of the first grouped optical member 411. In this case, the maskmember 560 for blocking an unwanted light beam and two second resilientmembers 490 are disposed between the first grouped optical member 411and the regulation member 460. The two second resilient members 490 arein contact with either side of the surface of the first grouped opticalmember 411.

The mask member 560 has an opening through which the first groupedoptical member 411 is exposed. The mask member 560 prevents the imaginglight beam from entering an area other than the opening. Thus, theimaging light beam is not made incident on the image pickup element 33from the peripheral portion of the first grouped optical member 411, andtherefore, an occurrence of ghosting caused by a reflected light beamcan be prevented.

The second resilient member 490 urges the first grouped optical member411 towards the lowpass filter holding member 420. Like the firstresilient member 480, the second resilient member 490 is formed from anelastomer. The second resilient member 490 allows the first groupedoptical member 411 to tilt from a plane perpendicular to the imaginglight beam, but restricts the inclination of the first grouped opticalmember 411 to be equal to or less than predetermined angle. In addition,the second resilient member 490 prevents the first grouped opticalmember 411 from being damaged by the vibration.

The regulation member 460 is formed from, for example, a conductivemetallic plate. Like the mask member 560, the regulation member 460 hasan opening through which the first grouped optical member 411 isexposed. Either side of the regulation member 460 is extended and isbent to form a latching tip. A latching hole 460 a is formed in each ofthe latching tip. By engaging the latching hole 460 a with a claw member420 c formed on the side surface of the lowpass filter holding member420, the regulation member 460 can be assembled to the lowpass filterholding member 420. Thus, the regulation member 460 restricts the motionof the first grouped optical member 411 in the imaging light axisdirection. That is, the regulation member 460 prevents the first groupedoptical member 411 from moving outside the lowpass filter unit 470 andfrom tilting at a predetermined angle or more for any reason.

In addition, an arm portion 460 c of the regulation member 460 issecured to the image pickup element holding member 510 by a screw 550.The arm portion 460 c has a rectangular shape having a width less thanor equal to a half of the length thereof. The arm portion 460 c iscurved at a middle portion in the length direction. Such a structureprevents the vibration of the first grouped optical member 411 thatfollows the expansion and contraction of the piezoelectric element 430from being directly transferred to the image pickup element holdingmember 510.

The image pickup element holding member 510 is grounded to the bodychassis 300 via a grounding member (not shown). Accordingly, by formingthe image pickup element holding member 510 and the body chassis 300using a conductive material, such as a metal, the regulation member 460can be grounded to a potential that is the same as that of the bodychassis 300 via the arm portion 460 c.

Furthermore, the second resilient member 490 is formed from a resilientand electrically conductive elastomer. A protrusion 490 a is formed onthe surface of the second resilient member 490 that is in contact withthe mask member 560. An opening 560 a is formed in the mask member 560so as to correspond to the protrusion 490 a formed on the secondresilient member 490. An adhesive layer is formed on each of the entirefirst and second surfaces of the mask member 560.

The mask member 560 is positioned so that a positioning reference hole560 b is aligned with a positioning reference hole 460 b of theregulation member 460. Thereafter, the mask member 560 is bonded to theregulation member 460. In addition, the second resilient member 490 ispositioned so that a positioning reference hole 490 b is aligned withthe positioning reference hole 560 b of the mask member 560, so that thepositioning reference hole 490 b is aligned with the positioningreference hole 460 b of the regulation member 460. Thereafter, thesecond resilient member 490 is bonded to the mask member 560.

In this case, since the protrusion 490 a of the second resilient member490 is formed at a location corresponding to the position of the opening560 a of the mask member 560, the protrusion 490 a extends through theopening 560 a and contacts the regulation member 460. That is, thesecond resilient member 490 is grounded to a potential that is the sameas that of the body chassis 300 via the protrusion 490 a and theregulation member 460.

Consequently, the surface of the first grouped optical member 411 thatis in contact with the second resilient member 490 is grounded, andtherefore, an attraction force caused by static electrical charge thatattracts dust or dirt to the surface of the first grouped optical member411 is decreased. As a result, a foreign substance, such as dust ordirt, deposited on the surface of the first grouped optical member 411can be easily removed using the vibration of the first grouped opticalmember 411 that follows the extraction and contraction of thepiezoelectric element 430.

As shown in FIG. 6, the second grouped optical member 412, one of thecomponents of the lowpass filter unit 470, is assembled on the lowpassfilter holding member 420 on the photographer side and is bonded to thelowpass filter holding member 420. In this way, the second groupedoptical member 412 is assembled on the lowpass filter holding member 420on the side opposite to the first grouped optical member 411 so that acertain distance is provided between the second grouped optical member412 and the first grouped optical member 411. Thus, the vibration of thefirst grouped optical member 411 is not affected by the second groupedoptical member 412. In addition, because the first grouped opticalmember 411 and the second grouped optical member 412 are assembled onthe same component (i.e., the lowpass filter holding member 420), thenumber of components can be reduced, and therefore, the possibility of aforeign substance entering inside the camera due to a large number ofsealing parts can be reduced.

The lowpass filter unit 470 and the image pickup element unit 500 isconnected with a rubber sheet 520 therebetween using a step screw 530. Asurface of the rubber sheet 520 on the side of the image pickup elementunit 500 is in tight contact with the third grouped optical member 413,which is in tight contact with the imaging surface of the image pickupelement 33 and is secured to the imaging surface. A surface of therubber sheet 520 on the side of the lowpass filter unit 470 is in tightcontact with the frame portion 420 a of the lowpass filter holdingmember 420. Thus, a space between the lowpass filter holding member 420and the third grouped optical member 413 is sealed by the rubber sheet520. A space between the first grouped optical member 411 and thelowpass filter holding member 420 is sealed by the first resilientmember 480. Accordingly, a space formed between the first groupedoptical member 411 and the image pickup element 33 is sealed so thatentrance of a foreign substance, such as dust or dirt, can be prevented.

The step screw 530 connects the arm portion 420 b of the lowpass filterholding member 420 with the image pickup element holding member 510 witha step-screw rubber bush 531 therebetween.

As noted above, the lowpass filter unit 470 is connected to the imagepickup element unit 500 via the rubber sheet 520 and the step-screwrubber bush 531. Thus, the lowpass filter unit 470 and the image pickupelement unit 500 floatingly support each other through the elasticity ofthe rubber sheet 520 and the step-screw rubber bush 531. Accordingly,the vibration of the piezoelectric element 430 is not transferred to theimage pickup element unit 500.

While the present embodiment has been described with reference to therubber sheet 520, the present invention is not limited thereto. Anymaterial having air-tightness that prevents a foreign substance, such asdust or dirt, from entering inside the camera and vibration absorptioncharacteristic that prevents the vibration of the piezoelectric element430 from being transferred to the image pickup element 33 can beemployed. For example, a two-sided adhesive sponge tape or a gel sheethaving a certain thickness can be employed.

FIG. 7 is a front view of the image pickup unit 400 and the body chassis300 when the image pickup unit 400 is assembled on the body chassis 300.FIG. 8 is a longitudinal cross-sectional view of a camera including theimage pickup unit 400. As shown in FIGS. 7 and 8, the lowpass filterunit 470 including the first grouped optical member 411, thepiezoelectric element 430, the vibration transfer member 431, thebiasing member 440, and the biasing force transfer member 441 isdisposed at a location substantially the same as that of the bodychassis 300 in the imaging light axis direction. The body chassis 300has a body chassis opening 300 b formed therein. The lowpass filter unit470 is disposed at a location separated from the body chassis opening300 b by a predetermined distance. In this way, since the lowpass filterunit 470 and the body chassis 300 are disposed at substantially the samelocation in the imaging light axis direction, the size of the camera inthe thickness direction (the imaging light axis direction) can bedecreased.

In addition, the piezoelectric element 430 is disposed on the firstgrouped optical member 411 at a position on the side of the eyepieceunit 210 (the upper side) from the imaging light axis. The biasingmember 440 is disposed on the first grouped optical member 411 at aposition facing the piezoelectric element 430 (on the lower side).

To obtain stable vibration of the first grouped optical member 411, thebiasing force of the biasing member 440 should be uniform. To obtain auniform biasing force, it is effective to reduce a spring constant ofthe biasing member 440 when considering dimensional tolerances of thecomponents. Furthermore, to generate a biasing force that can make thevibration of the first grouped optical member 411 stable, the size ofthe biasing member 440 tends to be increased, compared with thepiezoelectric element 430.

Connectors and a battery container (neither is shown) are disposed atpositions close to the image pickup unit 400 in a horizontal direction(a left-right direction) of the camera in the vicinity of the imagepickup unit 400. Accordingly, if the piezoelectric element 430 and thebiasing member 440 are arranged on the first grouped optical member 411in the horizontal direction of the camera, the size of the camera body 1may be increased in the horizontal direction.

In contrast, as shown in FIG. 8, in widely used single-lens reflexcameras, in the vicinity of the image pickup unit 400 in a verticaldirection of the camera, although the eyepiece unit 210 is locatedimmediately above the image pickup unit 400 and close to the imagepickup unit 400, a space can be easily provided immediately beneath theimage pickup unit 400. This is because the focus detection sensor unit31 that performs focus detection using the imaging light beam led by thesub-mirror 30 is disposed on the opposite side of the imaging light axisfrom the eyepiece unit 210, and the focus detection sensor unit 31 iscontained in the lower section of the mirror box 5 and beneathsubstantially the center of the mirror box 5.

Accordingly, by disposing the piezoelectric element 430 having a smallvolume in the section on the side of the eyepiece unit 210 (in the uppersection) and disposing the biasing member 440 having a large volume inthe lower section, an increase in the volume above the body chassisopening 300 b can be minimized. Thus, the rigidity and strength of thebody chassis 300 can be efficiently maintained, and therefore, therigidity and strength of the camera body 1 can be maintained.Furthermore, an increase in the height of the eyepiece-unit locking unit300 a can be prevented while maintaining the supporting rigidity andstrength of the eyepiece unit 210. Consequently, the sizes of the camerain the vertical direction and the horizontal direction can be reduced.

The vibration of the first grouped optical member 411, which is one ofthe components of the optical lowpass filter 410, is described next.When the MPU 100 serving as a control unit performs control so as toapply a predetermined periodic voltage to the piezoelectric element 430,the piezoelectric element 430 vibrates such that the piezoelectricelement 430 expands and contracts in the vertical direction of thecamera, which is a direction perpendicular to the imaging light axis. Asshown in FIG. 9C, the vibration transfer member 431 and the biasingforce transfer member 441 are bonded and secured to the first groupedoptical member 411. The first grouped optical member 411 is disposed soas to be sandwiched by the piezoelectric element 430 and the biasingmember 440 in a direction in the same plane. Accordingly, the firstgrouped optical member 411 is in contact with the piezoelectric element430 via the vibration transfer member 431 at all times. Thus, thevibration of the piezoelectric element 430 is transferred to the firstgrouped optical member 411.

According to the present embodiment, the first grouped optical member411, which is a vibrated member, is a quartz birefringent plate having amonocrystalline structure. Since quartz has a crystal structure, quartzhas a high Q value that indicates the sharpness of resonance comparedwith glass, which is an amorphous material. Thus, the vibration is noteasily attenuated. That is, by using the first grouped optical member411 formed from a quartz birefringent plate, the first grouped opticalmember 411 can be more efficiently vibrated than that formed from glass.Therefore, most foreign substances, such as dust or dirt, deposited onthe surface of the first grouped optical member 411 can be efficientlyremoved. As can be seen from a concept diagram of a Q value shown inFIG. 10, the Q value is expressed by the following equation:

Q=1/ΔΩ  (1)

That is, let A_(max) denote the amplitude of vibration at a resonancefrequency Ω. Then, the Q value is defined as an inverse of a frequencywidth having an amplitude greater than or equal to A_(max)/√2.

FIG. 11 is a transverse cross-sectional view of the image pickup unit400. As shown in FIG. 11, the lowpass filter holding member 420 includesthe frame portion 420 a surrounding the first grouped optical member 411and the four arm portions 420 b for mounting the lowpass filter holdingmember 420 on the image pickup element holding member 510 that supportsthe lowpass filter holding member 420. A thickness ha of the frameportion 420 a is greater than a thickness hb of the arm portions 420 b.The cross-sectional bending rigidity of the frame portion 420 a ishigher than that of the arm portions 420 b. That is, the characteristicresonance frequency of the frame portion 420 a is higher than that ofthe arm portions 420 b. Accordingly, when the piezoelectric element 430vibrates the first grouped optical member 411 at around thecharacteristic resonance frequency of the frame portion 420 a, theeffect of the arm portions 420 b having a low characteristic resonancefrequency is small. Thus, the piezoelectric element 430 can efficientlyvibrate the first grouped optical member 411.

According to the present embodiment, each of the arm portions 420 blocated at one of four locations has a bridge shape so that the clawmember 420 c formed on the side surface of the lowpass filter holdingmember 420 does not interfere with the arm portion 420 b. In addition,each of the arm portions 420 b includes an arm portion opening 420 d.That is, the arm portion 420 b is connected to the frame portion 420 aat either side of the arm portion opening 420 d. Note that the need forthe arm portion opening 420 d can be eliminated or the arm portion 420 bmay be connected to the frame portion 420 a at one of the two sides ofthe arm portion opening 420 d. When the cross-sectional bending rigidityof the frame portion 420 a is higher than that of the arm portions 420b, the first grouped optical member 411 can be efficiently vibrated.

Additionally, since the cross-sectional bending rigidity of the armportions 420 b is lower than that of the frame portion 420 a, thevibration is attenuated by the arm portions 420 b. Accordingly,vibration transferred from the lowpass filter holding member 420 to theimage pickup element unit 500 via the arm portions 420 b can be reduced.

According to the present embodiment, as noted above, the arm portions420 b of the lowpass filter holding member 420 are engaged with theimage pickup element holding member 510 with the step-screw rubberbushes 531 therebetween using the step screws 530. More specifically, asshown in FIG. 13, the tops of the step-screw rubber bushes 531 protrudefrom the image pickup element holding member 510 towards the lowpassfilter holding member 420 so as to be engaged with the arm portions 420b of the lowpass filter holding member 420.

In addition, the rubber sheet 520 is disposed between the lowpass filterholding member 420 and the image pickup element holding member 510.

In this way, a force that is caused by the rubber sheet 520 to move thelowpass filter unit 470 away from the image pickup element unit 500matches a force that is caused by the step screws 530 to bring thelowpass filter unit 470 and the image pickup element unit 500 together.As a result, the lowpass filter unit 470 and the image pickup elementunit 500 floatingly support each other without being in contact witheach other such that the contraction of the step-screw rubber bushes 531matches the contraction of the rubber sheet 520.

The arm portions 420 b of the lowpass filter holding member 420 aredisposed at four corners of the frame portion 420 a having asubstantially rectangular shape so that the center of gravity of thepositions of the four frame portions 420 a is substantially the same asthe center of gravity of the first grouped optical member 411 in planecoordinates perpendicular to the light axis. Thus, even when thecontraction of the step-screw rubber bushes 531 is not equal to thecontraction of the rubber sheet 520, the inclination of the lowpassfilter unit 470 can be minimized.

In addition, the four corners of the frame portion 420 a have a highcross-sectional bending rigidity. Accordingly, the first grouped opticalmember 411 is efficiently vibrated.

FIG. 12A is a front view of the components including the vibrationtransfer member 431 and the biasing force transfer member 441. FIG. 12Bis a side view of the components including the vibration transfer member431 and the biasing force transfer member 441. The cross section of thevibration transfer member 431 has a substantially L shape. A surface 431a and a surface 431 b of the vibration transfer member 431 are incontact with the first grouped optical member 411, and the vibrationtransfer member 431 is bonded to the first grouped optical member 411.Similarly, the biasing force transfer member 441 has a substantially Lshape. A surface 441 a and a surface 441 b of the biasing force transfermember 441 are in contact with the first grouped optical member 411, andthe biasing force transfer member 441 is bonded to the first groupedoptical member 411.

Lengths A1 and A2 of a contact surface of the vibration transfer member431 that is in contact with the piezoelectric element 430 in the imaginglight axis direction and a direction perpendicular to the imaging lightaxis direction are greater than length B1 and B2 of a contact surface ofthe piezoelectric element 430 that is in contact with the vibrationtransfer member 431 in the imaging light axis direction and a directionperpendicular to the imaging light axis direction, respectively. Thatis, the contact surface of the vibration transfer member 431 is largerthan the contact surface (vibratory surface) of the piezoelectricelement 430. The entire contact surface of the piezoelectric element 430is in contact with the contact surface of the vibration transfer member431. Such a structure allows most of the force generated by theexpansion and contraction of the piezoelectric element 430 to betransferred to the first grouped optical member 411. In addition, thisstructure prevents a locally-concentrated load from being applied to thefirst grouped optical member 411.

Similarly, lengths C1 and C2 of a contact surface of the first groupedoptical member 411 in contact with the biasing member 440 in the imaginglight axis direction and a direction perpendicular to the imaging lightaxis direction are greater than length D1 and D2 of a contact surface ofthe biasing member 440 in contact with the biasing force transfer member441 in the imaging light axis direction and a direction perpendicular tothe imaging light axis direction, respectively. That is, the contactsurface of the biasing force transfer member 441 is larger than thecontact surface the biasing member 440. Thus, the entire contact surfaceof the biasing member 440 is in contact with the contact surface of thebiasing force transfer member 441. Such a structure allows most of thebiasing force of the biasing member 440 to be transferred to the firstgrouped optical member 411. In addition, this structure prevents alocally-concentrated load from being applied to the first groupedoptical member 411.

A bent portion 431 c of the vibration transfer member 431 having asubstantially L shape and a bent portion 441 c of the biasing forcetransfer member 441 having a substantially L shape are disposed on theside facing the image pickup element 33. Such a structure allows thethickness of the lowpass filter unit 470 in the imaging light axisdirection to be decreased.

According to the present embodiment, a metal having a coefficient oflinear expansion similar to that of the first grouped optical member 411is used for a material of the vibration transfer member 431 and thebiasing force transfer member 441. Therefore, the adhesive layersbetween the vibration transfer member 431 and the first grouped opticalmember 411 and between the biasing force transfer member 441 and thebiasing force transfer member 441 are not damaged by a shearing stresscaused by a thermal stress due to a change in temperature. Thus,separation of the vibration transfer member 431 and the biasing forcetransfer member 441 from the first grouped optical member 411 can beprevented.

In addition, by employing a material having low attenuation, such as ametal, vibrations can be efficiently transferred from the piezoelectricelement 430 to the first grouped optical member 411.

A maximum shearing stress F generated in the adhesive layers between thevibration transfer member 431 and the first grouped optical member 411and between the biasing force transfer member 441 and the first groupedoptical member 411 is expressed by the following equation:

F=GΔTL/2t(α₁−α₂)  (2)

where G denotes the modules of rigidity of an adhesive agent, ΔT denotesa change in temperature, L denotes a maximum length of the contactsurface, t denotes the thickness of the adhesive layer, α1 denotes thecoefficient of linear expansion of the vibration transfer member 431 andthe biasing force transfer member 441, and α2 denotes the coefficient oflinear expansion of the first grouped optical member 411.

As can be seen from equation (2), as a difference between thecoefficient of linear expansional of the vibration transfer member 431and the biasing force transfer member 441 and the coefficient of linearexpansion α2 of the first grouped optical member 411 is decreased, themaximum shearing stress F generated in the adhesive layers can bedecreased.

According to the present embodiment, the first grouped optical member411 is formed from a quartz birefringent plate having a rotation angleof zero degrees (i.e., the X-axis of the quartz crystal is parallel to ashort side of the first grouped optical member 411). In addition, thecoefficient of linear expansion of the first grouped optical member 411in the long-side direction thereof is in the range of about 10 to about12 (×10⁶)/° C. In contrast, the vibration transfer member 431 and thebiasing force transfer member 441 are formed from a ferritic stainlesssteel. The coefficient of linear expansion of the vibration transfermember 431 and the biasing force transfer member 441 is in the range ofabout 10 to about 12 (×10⁻⁶)/° C. Since a ferritic stainless steel haslow attenuation compared with a resin material having a similarcoefficient of linear expansion, the vibration transfer member 431 andthe biasing force transfer member 441 can efficiently transfer thevibration of the piezoelectric element 430.

The first grouped optical member 411 is formed from a quartzbirefringent plate having a rotation angle of 90 degrees (i.e., theX-axis of the quartz crystal is parallel to a long side of the firstgrouped optical member 411). The coefficient of linear expansion of thefirst grouped optical member 411 in the long-side direction thereof isin the range of about 13 to about 15 (×10⁻⁶)/° C. In this case, thevibration transfer member 431 and the biasing force transfer member 441should be formed from an austenitic stainless steel having a coefficientof linear expansion in the range of about 14 to about 17 (×10⁻⁶)/° C.

Alternatively, an aluminum alloy, a titanium alloy, a nickel alloy, anickel-iron alloy, a nickel-chromium-iron alloy, or anickel-iron-molybdenum alloy may be used for the vibration transfermember 431 and the biasing force transfer member 441. The reason whysubstantially the same coefficient of linear expansion is used is toprevent the vibration transfer member 431 and the biasing force transfermember 441 from being separated from the first grouped optical member411 when bonded using an ultraviolet-curable adhesive agent. That is, ingeneral, the camera is used in a temperature range from −10° C. to 40°C. The camera is designed so that the adhesive layers including theultraviolet-curable adhesive agent between the vibration transfer member431 and the first grouped optical member 411 and between the biasingforce transfer member 441 and the first grouped optical member 411 arenot damaged by a shearing stress due to a thermal stress caused by achange in temperature in that range.

In addition, when the vibration transfer member 431 and the biasingforce transfer member 441 are bonded to the first grouped optical member411, the occurrence of thermal stress should be avoided. Therefore, anadhesive agent curable at a room temperature can be used, not aheat-curable adhesive agent. According to the present embodiment, anultraviolet-curable adhesive agent is used. However, a two-liquid mixingadhesive agent or other adhesive agents curable in a room temperaturemay be used.

As noted above, the rubber sheet 520 seals between the lowpass filterholding member 420 and the image pickup element 33. In addition, thepiezoelectric element 430 and the first resilient member 480 sealbetween the first grouped optical member 411 and the lowpass filterholding member 420. Accordingly, a sealed space that prevents a foreignsubstance, such as dust or dirt, from entering is formed between thefirst grouped optical member 411 and the image pickup element 33.

Furthermore, the lowpass filter unit 470 including the first groupedoptical member 411 is configured so as to sandwich the rubber sheet 520with the image pickup element unit 500. Still furthermore, the lowpassfilter unit 470 is connected to the image pickup element unit 500 withthe step-screw rubber bushes 531 therebetween using the step screws 530.In this way, the vibration of the lowpass filter unit 470 is attenuatedby the rubber sheet 520 and the step-screw rubber bushes 531.Accordingly, the vibration is not transferred to the image pickupelement 33.

In such a structure, when the piezoelectric element 430 vibrates, thevibration has little negative impact on the image pickup element 33. Asa result, the structures subjected to the vibration can be limited. Thatis, only the first grouped optical member 411 that is desired to vibratecan be particularly vibrated. Accordingly, the total mass of thestructure subjected to the vibration can be reduced, and therefore, theenergy required for driving the piezoelectric element 430 can bereduced.

In addition, since little vibration of the first grouped optical member411 is transferred to the image pickup element 33, damage to the imagepickup element 33, such as separation of the image pickup element 33,can be prevented. Furthermore, when a shock is applied to the camera,very little of the shock is transferred to the piezoelectric element430. Thus, damage to the piezoelectric element 430 due to a shockapplied to the camera can be prevented.

As mentioned earlier, the first grouped optical member 411 (thevibration transfer member 431) is not bonded to the piezoelectricelement 430. That is, the first grouped optical member 411 is notcoupled with the piezoelectric element 430. Accordingly, when a periodicvoltage is applied to the piezoelectric element 430 and thepiezoelectric element 430 expands and contracts, the piezoelectricelement 430 generates only a force in a direction in which the firstgrouped optical member 411 is urged. A force in a direction in which thefirst grouped optical member 411 is pulled is not generated. Thus, evenwhen a high-frequency voltage in an ultrasonic range is applied to thepiezoelectric element 430, excess pulling force is not applied to thepiezoelectric element 430. Accordingly, damage, such as separation inthe layer portion, can be prevented.

An exemplary operation of removing a foreign substance, such as dust ordirt, deposited on the surface of the first grouped optical member 411according to the present embodiment is described next. When a useroperates the cleaning instruction operation member 44, the camerareceives a cleaning mode start instruction. Thus, the camera enters acleaning mode.

According to the present embodiment, the cleaning instruction operationmember 44 is provided to the camera. However, the present invention isnot limited thereto. For example, an operation member used forinstructing the camera to enter the cleaning mode is not limited to amechanical button. The operation member may be one for selecting aninstruction from a menu displayed on the color liquid crystal monitor 19using a cursor key or an instruction button. Alternatively, the cameramay automatically enter the cleaning mode in a normal operating sequenceof the camera, such as power-on and power-off operations of the camera.Alternatively, the camera may automatically enter the cleaning mode onthe basis of the number of image captures or a date and time.

The power supply circuit 110 supplies electrical power required in thecleaning mode to the components of the camera body 1. Concurrently, thepower supply circuit 110 detects the level of a battery of the powersupply unit 42 and sends the detected result to the MPU 100.

Upon receipt of a cleaning mode start signal, the MPU 100 sends adriving signal to the piezoelectric element driving circuit 111. Uponreceipt of the driving signal from the MPU 100, the piezoelectricelement driving circuit 111 generates a periodic voltage for driving thepiezoelectric element 430 and applies that periodic voltage to thepiezoelectric element 430. The piezoelectric element 430 expands andcontracts in accordance with the applied voltage.

When the piezoelectric element 430 expands, the first grouped opticalmember 411 is urged by the piezoelectric element 430 and is moved in adirection perpendicular to the imaging light axis (i.e., the surfacedirection). The biasing member 440 contracts by the amount of movementof the first grouped optical member 411. The optical member 411 is urgedtowards the piezoelectric element 430 by the biasing member 440.Accordingly, when the piezoelectric element 430 contracts, thepiezoelectric element 430 moves while following the contraction of thepiezoelectric element 430.

When the periodic voltage is applied to the piezoelectric element 430,the above-described movement is repeated. The optical member 411vibrates in accordance with the periodic expansion and contraction ofthe piezoelectric element 430. The vibration of the first groupedoptical member 411 allows a foreign substance, such as dust or dirt,deposited on the surface of the first grouped optical member 411 to beremoved.

According to the present embodiment, in order to cause the secondresilient member 490 to be grounded to the regulation member 460although the non-conductive mask member 560 is present, the opening 560a is formed in the mask member 560. However, the present invention isnot limited thereto. That is, it is only required that the mask member560 does not interfere with the protrusion 490 a of the second resilientmember 490. For example, a notch may be formed in the mask member 560,and the protrusion 490 a of the second resilient member 490 may be incontact with the regulation member 460 through the notch.

In addition, the mask member 560 and the adhesive layers may be formedfrom an electrically conductive material. In this case, even when theprotrusion 490 a is not formed on the second resilient member 490, thefirst grouped optical member 411 can be grounded to a potential that isthe same as that of the body chassis 300 via the second resilient member490, the adhesive layers, the mask member 560, and the regulation member460.

In addition, when the mask member 560 is not necessary, an adhesivelayer having an opening may be formed on the regulation member 460 orthe second resilient member 490, and the regulation member 460 may begrounded to the second resilient member 490 through the opening.Alternatively, a conductive adhesive layer may be formed on theregulation member 460 or the second resilient member 490, and theregulation member 460 may be grounded to the second resilient member490.

Furthermore, a two-sided adhesive tape may be adhered to the surface ofthe regulation member 460 on the side facing the second resilient member490 so as to partially overlap the second resilient member 490. Thesecond resilient member 490 may be grounded to the regulation member 460at a location at which the two-sided adhesive tape does not overlap withthe second resilient member 490. Alternatively, a conductive two-sidedadhesive tape may be adhered to the surface of the regulation member 460on the side facing the second resilient member 490 so that at least partof the two-sided adhesive tape overlaps the second resilient member 490.Thus, the second resilient member 490 may be grounded to the regulationmember 460.

In addition, while the present embodiment has been described withreference to the second resilient members 490 having a long and thinplate shape and disposed at two locations, the second resilient member490 have a ring shape can be used. Furthermore, while the presentembodiment has been described with reference to a conductive elastomeras the material of the second resilient member 490, the presentinvention is not limited thereto. Any polymeric material havingelectrical conductivity and elasticity can be used.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures and functions.

This application claims the benefit of Japanese Application No.2006-198596 filed Jul. 20, 2006, which is hereby incorporated byreference herein in its entirety.

1. An image pickup apparatus having an image pickup element configuredto convert an optical image of an object into an electrical signal,comprising: an optical member disposed in front of the image pickupelement, the optical member being separated into a plurality of groupedsub-optical members in an imaging light axis direction; and a vibratingunit configured to vibrate a first grouped sub-optical member disposedat a forefront position in the optical member, wherein the first groupedsub-optical member is formed from a monocrystalline plate.
 2. The imagepickup apparatus according to claim 1, wherein the monocrystalline plateis a quartz birefringent plate.
 3. The image pickup apparatus accordingto claim 1, wherein a surface of the monocrystalline plate is coated soas to provide optical functionality.
 4. The image pickup apparatusaccording to claim 3, wherein the optical functionality includesreflection of at least one of an infrared light beam and an ultravioletlight beam.
 5. The image pickup apparatus according to claim 1, whereina second grouped sub-optical member of the optical member is disposed onthe side of the first grouped sub-optical member close to the imagepickup element, and wherein the second grouped sub-optical memberincludes at least one of a birefringent plate, a phase plate, and aninfrared absorption glass.
 6. The image pickup apparatus according toclaim 1, wherein a third grouped sub-optical member of the opticalmember is integrally bonded and secured to the image pickup element. 7.The image pickup apparatus according to claim 3, further comprising aholding member configured to hold the first grouped sub-optical memberand the second grouped sub-optical member.
 8. The image pickup apparatusaccording to claim 1, wherein the vibrating unit vibrates the firstgrouped sub-optical member in a direction perpendicular to the imaginglight axis.
 9. An image pickup unit included in an image pickupapparatus, comprising: an image pickup element configured to convert anoptical image of an object into an electrical signal; an optical memberdisposed in front of the image pickup element, the optical member beingseparated into a plurality of grouped sub-optical members in an imaginglight axis direction; and a vibrating unit configured to vibrate a firstgrouped sub-optical member disposed at a forefront position in theoptical member, wherein the first grouped sub-optical member is formedfrom a monocrystalline plate.
 10. The image pickup unit according toclaim 9, wherein the monocrystalline plate is a quartz birefringentplate.
 11. The image pickup unit according to claim 9, wherein a surfaceof the monocrystalline plate is coated so as to provide opticalfunctionality.
 12. The image pickup unit according to claim 11, whereinthe optical functionality includes reflection of at least one of aninfrared light beam and an ultraviolet light beam.
 13. The image pickupunit according to claim 9, wherein a second grouped sub-optical memberof the optical member is disposed on the side of the first groupedsub-optical member close to the image pickup element, and wherein thesecond grouped sub-optical member includes at least one of abirefringent plate, a phase plate, and an infrared absorption glass. 14.The image pickup unit according to claim 9, wherein a third groupedsub-optical member of the optical member is integrally bonded andsecured to the image pickup element.
 15. The image pickup unit accordingto claim 11, further comprising a holding member configured to hold thefirst grouped sub-optical member and the second grouped sub-opticalmember.
 16. The image pickup unit according to claim 9, wherein thevibrating unit vibrates the first grouped sub-optical member in adirection perpendicular to the imaging light axis.